1. Field of the Invention
The present invention broadly relates to aircraft escape systems and, more particularly, is concerned with a self-deploying afterbody apparatus on an ejection seat for stabilizing the seat and reducing aerodynamic drag thereon following an emergency ejection.
2. Description of the Prior Art
The effect of abrupt deceleration on a crewmember is particularly acute during bail-out from an aircraft flying at supersonic speeds. The inertial forces to which the ejection seat occupant is subjected during the deceleration period immediately following ejection are equivalent to many times the forces of gravity and are often beyond human endurance.
Consequently, over the past few decades a common objective has been to devise an aircraft escape system which appreciably reduces the drag forces imposed upon the seat and its occupant when suddenly thrust into the airstream, thereby producing a much less severe deceleration than heretofore. Several approaches to achieving this objective have appeared in the prior art.
U.S. Pat. No. 2,829,850 to Culver employs a skip-flow generator which is projected in front of the seat to generate an aerodynamic skip-flow around the blunt body of the ejection seat and its occupant. U.S. Pat. No. 2,931,598 to Sanctuary uses rockets on the rear of the seat to force the seat into an optimum low drag attitude by causing tilting of the seat about a transverse axis in a backward direction. Both of these patents disclose additional lateral fin features for stabilizing the seat against both rotation and oscillation (pitch and yaw) after ejection has taken place. However, the approaches of these two patents envision escape systems which are too complex mechanically, making them prone to reliability problems, and add considerable weight to the aircraft.
More recently, ejection seats equipped with afterbodies have been shown through wind tunnel tests and computer simulations to reduce yaw and pitch excursions as well as the longitudinal deceleration experienced by the seat and occupant during high speed emergency escape from the aircraft. U.S. Pat. No. 4,261,535 to Swanson provides an afterbody in the form of a plurality of inflatable air bags on the back of the ejection seat. Gas generators cause the air bags to inflate in sequence from top-to-bottom as the seat and its occupant eject from the aircraft. This produces a rearwardly extending generally streamline afterbody which is said to reduce aerodynamic drag and stabilize the seat with its occupant after emergency ejection.
While the improved aerodynamic characteristics of afterbodies on ejection seats offer the potential for prodviding a safer environment for the occupant of the seat by reducing the risk of injuries due to limb flail and lateral and/or longitudinal movement of internal organs, certain problems connected with afterbodies must be overcome. A primary constraint in employing afterbodies has been the physical problems in deploying the afterbody from the ejection seat during emergency escape. The afterbody should be in place and effective by the time the last rollers of the seat exit the ejection rails. The afterbody of Swanson fails to overcome this constraint. By the time the seat leaves the aircraft, the upper air bags of the afterbody are fully inflated; however, the lower bags are only partially inflated. Not until after the lower bags are completely filled will the total afterbody stabilize the seat and reduce aerodynamic drag.
Consequently, a need exists for an improved aircraft escape system which is simple in design, reliable in operation and effective when needed, characteristics which are lacking in the prior art systems.